Rear a/c changes temp without command

[carrmann]

Hey all, truck has done this a few times. Never stuck around though for me to troubleshoot. The rear ac usually blows nice and cold... well suddenly today it started blowing hot(heated) air. Turned off rear ac, front blows cold the whole time. I checked the controls front/rear and they were set properly. Turned it off/then on, including the truck itself. This did not fix the problem. Could it be a blend door calibration issue? After it sat for a bit, the ac blew cold again in the rear for about 3 minutes then started blowing hot again. I'm guessing blend door, but curious if it could be something else I'm not aware off?

Any tips/suggestions? this is a 2007 yukon xl denali, roughly 170k miles.

Thanks!

 

[mikez71]

It could also be the control unit itself.
Do you have auto or manual climate controls?
(Mine is manual and the rear temp and mode were acting up.)

Best to scan for any codes as well.

 

[Joseph Garcia]

Do you have access to a quality bi-directional scanner? That would help you troubleshoot your issue, without resorting to the parts cannon.

 

[carrmann]

Yes, I have a tech 2. I'll check for codes for that. I forgot this can have codes for stuff like that. Oops.

It does have the 'auto' function on the control in the front climate control.

I disconnected the wire to the blend door actuator (middle of the rear hvac assembly blend door actuator, not the front one that controls roof or feet). So far the problem hasn't come back since. We will see! Lol.